Apparatus for sighting guns



35 iras-33 RUM m June 29 1926.

S. L. G. KNOX APPARATUS FOR SIGHTING GUNS Filed Dec. 27, 1922 2 sheets-sheet 2 1N VENToR ATTORNE Ys N. EE; i

Patented June 29, 1926.

UNITED STATES PATENT OFFICE.

APPARATUS FOR SIGrI-ITING GUNS.

Application filed December 27, 1922. Serial No. 609,359.

My invention relates to apparatus for sighting guns and has particular reference to methods and apparatus for correcting errors in sighting naval guns caused by the tilting of the axis of thetrunnions out of a horizontal plane by the rolling and pitching of the ship.

When a naval gun, as ordinarily mounted and sighted, is fired at an angle of elevation other than zero, it is necessary that the axis of the trunnions of the guns be horizontal in order that the plane 0f the trajectory of the gun shall be that indicated by the gun sights. Errors in sighting are introduced whenever the trunnions are not horizontal and the gun is elevated. These errors are so slight at low angles of elevation and for the angles of trunnion tilt likely to occur when firing off the broadside that, though Well known theoretically and treated mathematically in text-books, they have not, until a relatively recent date, been considered to have any importance in practice. The necessity in war of sometimes firing at long ranges ahead and astern has now given the question a practical importance not previously realized.

When a naval gun is pointed approximately ahead or astern the axis of its trunnions points athwartship, and is therefore tilted by the roll of the ship, which is generally much greater than the pitch, which causes the tilting of the trunnions when the gun is pointed abeam. As there is no difference in principle, but merely in degree, between the effects of roll, pitch, or a combination of both, all of these conditions will be hereinafter referred to as roll.

The theory of the sighting of naval guns has heretofore been based on the assumption that the axis of the bore of the gun always lies in a vertical plane having a fixed relation to another vertical plane passing through the line of sight. This is true, however, only if the trunnions of the gun do not tilt, and the trunnions do tilt whenever the ship rolls. The effect of this combined tilting and elevation can, under modern conditions of warfare, become so Igreat as to cause an error in deflection, azimuth, of a mile or more, in the case of a large gun fired at long range in a rough sea, and trained within approximately 30 of the longitudinal axis of the ship. Since this error changes from extreme right to extreme left within a few seconds as the ship rolls from side to side it cannot be corrected by spotting, as the trial and error system applied to the correction of other errors of gun fire is called.

When the bore of the gun is elevated with reference to the line of sight, and the trunnions are tilted, the roll of the ship causes the axis of the bore to generate a segment of the surface of a cone having as its axis a horizontal line corresponding t0 the axis of the bore of the gun when in the horizontal position, that is, at 0 elevation. This introduces two errors into the sighting of the gun not heretofore compensated for; one the error in azimut-h or deflection before referred to and the other an error in elevation of the gun.

Referring first to the error in azimuth; as

naval guns sights are ordinarily arranged, the telescope points along a line approximately parallel to the axis of the gun, and this line of sight is not varied if and as the bore of the gun moves back and forth on the surface of the cone due to the combined effect of trunnion tilting and elevation. The line of sight is supposed to indicate the plane of the trajectory, so that, if the line of sight terminates in a target it is assumed that the projectile will hit the target or at least fall along the line of sight, whatever the elevation of the gun. The plane of the trajectory, however, swings back and forth through an angle equal to the projection on a horizontal plane of the conical segment generated by the axis of the bore of the gun as the trunnio-ns are tilted. But the line of sight does not change. It therefore lies in the plane of the trajectory only when the trunnions are horizontal, although the assumption has been that it lies in the plane of the trajectory under all conditions.

The second error caused by the tilting of the trunnions, the error in the elevationA of the gun, is not ordinarily corrected at present because the angle of elevation at which to set the gun, is calculated for that position of the gun at the very peak of its path in generating the segment of the surface of the cone. But the angle of elevation does not remain at this value. It grows less as the gun swings by the peak position to either lett or right, the error being greatest when the gun is at the ends of its swing.

By my present invention I correct both of these errors first by continuously adjusting the line of sight to lie in a plane parallel to the plane of the trajectory, and then by adjusting the line of sight in the first mentioned plane by a proper amount to compen sate for the dipping, or reduction of elevation, of the gun as it swings by the peak or point of maximum elevation as the trunnions are tilted.

My invention provides means for indicating at all times the angle by which the lintV of sight must be swung to the left or right, as the trunnions tilt more o-r less, in order that it may always lie in a plane parallel to the plane of the trajectory, or, alternately, my invention provides means for indicating at all times the amount of the error in azimuth, without shifting the line ot sight, in order that the gun or guns may not be tired when the error caused by the tilt of the trunnions is more than a predetermined amount. Means are therefore provided for indicating at all times the departure of the axis of the trunnions Yfrom the horizontal, and the consequent tilting of the plane of the trajectory. One way of doing this is to sight to the horizon on a line parallel to thwaxsofitliimtriinnions; another way is to Wippe; and another 1s to establish tie re erence plane byihckuse of apen-- dulum oithedead-Wbeat type. Means for a Justing the line ot sight angularly with respect to the axis ot the bore of the gun allow the line of sight to be moved both into the reference plane, to cause it to lie parallel to the plane of the trajectory, and through a vertical angle sufficient to compensate for the reduction in the angle of elevation o'f the gun caused by the tilting of the trunnions.

Itis not necessary that the reference plane should be established with absolute accuracy. Even at high angles of elevation the error in azimuth caused by a trunnion tilt of less than 1 is practically negligible, so that an apparatus which corrects, or indicates an error equivalent to less than 1 tilt of the trunnions is sufficiently accurate. There is no difficulty in establishing the reference plane with much less than 1 of error by any of the means ust mentioned.

My present invention further comprises the novel structure, combination of parts and features described below, for a. clear understanding of which, reference will be made to the accompanying drawings in which: v

Fig. l is a view in side elevation of a naval -gun lprovided with the apparatus of my invention.

Fig. 2 is a plan View of this gun.

Fig. 3 is an enlarged view of the connection between the outer end of the sight rod and the sight yoke.

Fig. 4 is an end View ot the pendulum .indcator and reference point in operative relation.

Fig. 5 is View of a modied form of pendulum indicator.

Figs. 6 and 7 show the pendulum indicator modilied for electric lire control, and

Figs. 8, 9 and 10 are explanatory diagrams, Fig. 8 showing in elevation the angular relationship between the line ot sight and the axis of the gun bore; Fig. 9 representing these relationships as seen in plan view; and Fig. l0 as seen in end view.

With reference first to Figs. S, 9 and l0 of these drawings, the axis of the bore of a gun, which by way of example, is assumed to be trained directly ahead or astern ot the ship and pointed at Oo elevation is represented by the line AB. The line of sight CD lies parallel to the axis AB. Under these conditions the tilting of the plane of the trunnions will not cause the axis AB to be taken ott from the target.

Assuming that the plane of the trunnions TT, Figure l0, remains horizontal, it the gun is elevated through an angle a so that the axis AB assumes a position AB the line of sight CD remains approximately horizontal and, if angle a has been cory rectly calculated for the range, wind resistance and other factors usually taken into consideration, the projectile fired from the gun in this position should hit the target or at least fall within the plane ot the line of sight.

Should the ship be moving in a ,fairly heavy sea, however, the plane ot the trunnions TT will not remain horizontal, but will be continuously oscillating from port to starboard through a certain angle ot roll with respect to the horizontal. Assuming that the plane ot the trunnions is tilted through an angle of roll ZJ (Fig. l0) to a position TTH and that the gun is elevated by an angle a, the axis o'l" the bore AB will assume the position AB and will make an angle c (Fig. 9) with respect to the Vertical plane through the axis AB; that is, with respect to the vertical plane through the axis oit the bore with the trunnions horizontal. It the gun is tired in this position the plane of the trajectory will be a substantially vertical plane through the line AB, and the projectile will fall widc to the right ot the target, because the line of sight CD which passes through the target still remains in a horizontal plane and has not been shifted in this plane to compensate for angle 0. In order to correct for this error in azimuth, which amounts to the angle c, I establish a reference plane into which the line of sight CD may be adjusted to determine the value of the angle c through which the axis of the bore ot the gun must be rotated in order to train the gun back onto the target.

This reference plane may be conveniently established by means of a pendulum of the dead beat type arranged with an indicating pointer mounted on an axis parallel to the axis ot' the gun bore. This indicator, therefore, will always remain in a vertical plane parallel to another vertical plane through the axis of the bore of the gun and hence parallel to the plane ot the trajectory.

This pendulum indicator will therefore establish the point D, when the trunnions are tilted to the angle and the line of sight may easily be brought to lie in this reference plane by adjusting it to the position CD. This will cause the line of sight to be taken olf of the target, or, in other words, the cross hairs of the sighting telescope will move away from the target. T the gun is now trained to bring the cross hairs back onto the target, the axis of the bore of the gun will be rotated through the angle c, from the position A B to the position AB, and will again be trained in the plane of the target.

Inasmuch as the axis of the bore of the gun sweeps the surface of a segment as a cone as above described, when the trunnions are tilted by the roll of the ship, the angle of elevation a will be reduced in value to the angle am (Fig. 8). In order to correct for this change in elevation of the gun, the line of sight CD may now be moved, in a vertical plane, through an angle equal to the dierence between angle a and angle 6W to the position CD. This will again cause the cross hairs of the sighting telescope to move off from the target and, in bringing them back on to the target, the angle of elevation of the gun will be brought back to the correct value, angle a These adjustments to correct for errors caused by trunnion tilt may be made in separate steps, as they have been described above, for the sake of clearness, or they may be made simultaneously, inasmuch as there is a dei'inite, iixed relation between the change of angle of azimuth, or horizontal angle, and the change of angle of elevation, or vertical angle.

Referring now to Figs. 1 and 2 of the accompanying drawings, the gun base 10 supports the framework 1l on the usual vertical bearing so that it may be freely moved about this bearing, thru any horizontal angle desired. by means of the training handwheel 12. The framework 11 carries trunnion bearings in which the trunnions 13 on the gun mount 14 are carried and provision is i Tratta made for rotating the gun about trunnions 13, thru any vertical angle desired, by means of the pointing handwheel 15. The gun barrel 16 slides in the gun mount 14 when the gun is discharged, the recoil being taken up by recoil pistons and cylinders located in the lower part oit the gun mount.

The sight yoke 25 is universally mounted, over the center of the gun mount, this universal mounting including two horizontal pivots 17, secured to bosses 13, on the gun mount, and the single vertical pivot 19, on the intermediate member 20. The sight yoke 25, accordingly, may be moved in either a horizontal or a vertical plane in order to make proper adjustment both in azimuth and elevation for the factors for which such adjustments are customarily made; such as range, speed of enemys ship, speed of own ship, wind resistance, dritt, etc.

The mechanism for controlling the movement of the sight yoke to make these adjustments comprises the sword 21 carried in a curved slide called the scabbard which is fixed to a bracket on the gun mount 14, the curvature of the slide being determined by an arc struck from the pivot 17 as a center, so that, as-the sword 21 is moved in a vertical plane by means of the adjusting handwheel 22, it will move in the arc of the circle having the pivot 17 as its center. In the head 23 of the sword there is a pair of curved ways 24, cut on the segment ot a circle about the pivot 19 as its center. The extension head 26 on the sight yoke 25 has ways cut in the lower surface thereof to coact with ways 24 in the sword head 23; and adjusting wheel 27 which operates feed screw 28, passing through a nut 29 in the sight yoke extension, provides means for moving extension head 26 in a horizontal plane along the ways 24. By means ot' this mechanism the sight yoke 25 may be readily adjusted in both a horizontal and a vertical plane by rotating the handwheels 22 and 27. These handwheels are operated by the sight setter.

Up to this point the entire mechanism ot the construction of the gun is of the ordinary type in common use. In accordance with my invention I mount the gun trainers telescope 30, and the gun pointers telescope 31, upon sight rods 32 and 33 which are universally mounted upon the sight yoke 25 so that the sight rods, and consequently the telescopes, may be adjusted in either a horizontal or a vertical plane with respect to the sight yoke. This universal mounting comprises intermediate members 34 and 34', having vertical bearings 35 and 35 in brackets extending from the sight yoke, and provided with biturcated heads 3G and 36 adapted to receive the small trunnions 37 and 37 on sight rods 33 and 32 respectively. A connecting rod 38 transmits the motion of sight rod 33 to sight rod 32 so that the axes of these rods always remain in parallel relation to each other.

it the outer or left hand end of sight rod 33, a forked member 39 (Figs. 3, 2 and l) partially embraces the sight rod and pivotally connected thereto by a pair of horizontal bearings 40. The lower end of forked member 89 is secured by a ball and socket joint 4l to a fixed point on the sight yoke 25 (see Fig. l). The outer end of sight rod 32 is connected in a similar manner t-o another l'xed point on sight yoke 25. By means of' this arrangement the simultaneous adjustment for correction for errors in azimuth and elevation is secured, since any rotation o'll sight rods 33 and 32 about pivots 35 and 35 resj'iectively will cause a vertical depression of the outer end of the sight rod, depending upon the amount of horizontal movement given to the sight rod.

In order to give the proper horizontal movement to sight rod to keep its axis in the reference plane established by the pendulum indicator, to be later described, a sight rod extension 42 is rigidly attached to the sight rod, as by means of the projections 43, and extends rearwardly, terminating in a lateral projection 44 on which is mounted a reference point 45, transversely adjustable on projection 44 by means ot slide 59 and its coojierating screw GO and handwheel 6l, in order to correct for the angle of deflection received from the firecontrol room. A scale 62 on projection 44 indicates the amount of adjustment of slide 59. rlhe movement of the sight rod is controlled through the adjusting wheel 46, mounted near the end of extension 42 and provided with the screw 47 which coacts with a nut 48 carried on sight yoke 25. A dead beat pendulum49 contained in an appropriate housing is so mounted that its pendulum axis 50 is located in a vertical plane parallel to the vertical plane through the axis of the gun bore, and that reference point 45 will be opposite axis 50 when the gun is pointed at Oo elevation. The pendulum will then indicate a reference plane parallel to the plane of the trajectory, under all conditions ol trunnion tilt. The motion ot the pendulum is transmitted to a pendulum indicator 51 4which is located in proximity to the reference point 45 and which may conveniently be, curved into the arc of a circle so as to remain at about the same distance from reference point 45 for all angles of elevation oit the gun. lith the trunnions of the gun horizontal, in which position they are represented in Fig. 2, pendulum indicator 51 will be in mid-position.

lVhen the gun is to be fired under conditions where trunnion tilting` does not have to be taken into account, as, for example, when the sea is smooth, slide 59, carrying reference point 45, is set in the mid-position of scale 62, and the sight setter adjusts sight yoke 25 by means ot' hand wheels 22 and 27, for the angles olf elevation, and deflection (azimuth) which he receives from the lire-control room, just as he would do it the gun were not equipped with appara tus for compensating for trunnion tilt. The gun is then sighted on the target and fired.

lVhen, however, the gun is to be fired while the ship is in a heavy sea, under conditions where it is desirable to compensate l'or trunuiml tilting, the sight setter adjusts sight yoke hy hand wheel 22 for the angle ot elevation received from the lire-control room, and he turns handwheel 27 to place sight yoke 25 in the mid-position of its azimuth scale on sword head 23. He then manipulates handwhecl (3l to set reference point 45 to the right or lejft of the midposition of scale G2 by the angle of azimuth received from the lire-control room.

'lhe gun trainer looking through telescope 230 and actuating handwheel l2, and the gun pointer looking through telescope 3l and operating halulwheel l5, keep the cross hairs of the telescopes upon the target. A fourth man now manipulates handwheel .lo so as to keep reference point 45 in align ment with the pendulum indicator 5l, following this indicator as it swings back and 'lortli upon its axis 50. The motion o'l indicator 5l is only apparent because.` actually, it always remains in a plane parallel to the plane of the trajectory` It is the gun itself which really swings with reference to pendulum indicator 5l. lVhen the fourth man turns handwheel 4G to keep reference point 45 in alignn'ient wit-h the pendulum indi- Gator, he causes the sight rod 3?) to more transversely with reterence to sight yoke in one direction or another. so that its axis, and therefore the line ot sight through the telescopes, always lies in the reference plane established by pendulum indicator 5l, which is a vertical plane parallel to the vertical plane passing through the axis of the gun bore-the plane ol the trajectory.

As sight rod lf moved transversely with reference to sight yoke the mechanisn'i illustra ted in Fig. 3, for connecting the outer end ot the sight rod to a fixed point on sight yoke causes the outer end ol the ght rod to be automatically depressed by a. predetermined amount depending upon the amount o lateral nioven'ient ot the sight rod. This depression ot the end ot the lsight rod 93 about the horizontal axis 37 compensates ttor the reduction in elevation ol the gun caused by the tilt of the trunnions. rlhe movement oit the line of sight with respect to sight yoke 25 caused by the operation olf luuidwheel 46 throws the cross hairs oli the telescopes off oli the target, and the gun trainer and gun pointer, by operating the handwheels 12 and 15 respectively, immediately bring their cross hairs back on the target and, if the gun is now tired, the plane of the trajectory will be parallel to the plane of the line of sight, and the gun will be re-elevated to the proper angle and the projectile will therefore hit the target.

In case it is thought unnecessary to compensate for the error in elevation of the gun caused by the tilting of the trunnions, the reference point 45, may be. mounted directly on sight yoke 25, means, such as slide 59 and handwheel 61, being provided for its adjustment. Telescopes 30 and 31 may then be mounted on the sight yoke in the ordinary manner, and the mechanism illustrated in Fig. 3 for depressing the outer end of the sight rod, as well as all of the mechanism for causing motion of the telescopes relative to the sight yoke 25, may be dispensed with. This simplifies the apparatus, the movement of the line of sight to keep it in the reference plane of the pendulum indicator being secured by means of the handwheel 27.

In practice it may be found too difficult, or too expensive, to constantly shift the line of sight back and forth to keep the reference point 45 in the plane of the pendulum indicator 51 and/or to shift the gun in azimuth with sufficient speed to keep the telescope on the target. For this reason I provide the alternative means for preventing errors caused by trunnion tilt, which consists in indicating at all times the amount of error in azimuth existing by virtue of the tilting of the trunnions, so that the gun or guns may not be fired when this error is more than a predetermined amount. For this purpose I mount on the pendulum indicator 51 a plate 52 (Fig. 5), which may conveniently be made of transparent material, and on which is drawn a diagram so constructed as to indicate the permissible limits of error at various angles of elevation of the gun.

In constructing this diagram the vertical center line 50-53 is placed in the plane of the indicator 51, and various horizontal lines 53 to 58 inclusive are drawn at such heights above the pendulum axis 50 that the reference point 45 will fall on them at certain chosen angles of elevation of the gun, say, for example, at 3, 6, 9, 12 and 15 respectively. Assuming that reference point 45 falls on line 54 at 3 elevation; on line 55 at 60 elevation; etc., then a distance is measured @if horizontally on line :54, on each-side of the center line 50-53, such that, if the Areference point 45 is allowed to deviate further from the center line than the amount so laid off, there will be an error in azimuth, at the range corresponding to 3 elevation equal to more than the permissible maximum error in azimuth, say for example 100 yards. A distance corresponding to this predfte-rmined permissible maximum error in yards is then laid off for each of the chosen angles of elevation, and through the points so found, the curves WX and YZ are traced, forming the boundaries of the transparent plate 52.

W hen this alternative means of eliminating the errors caused by trunnion tilt is adopted, reference point 45 is mounted in fixed position on sight yoke 25, the sights are used as ordinarily mounted and with no attempt to oscillate the telescopes so as to compensate for the errors of trunnion tilt, but merely to indicate, by the movement of the reference point 45 back and forth across the lines IVX and YZ, the times when the error is within or without the maximum permissible limits.

By mounting a plate 63 (Figures 6 and 7 of insulating material, on the pendulum indicator 5l, and providing on one surface of this plate an insert 64 of electrically conducting material, the shape of the insert 64 being determined by the curves WX and YZ, and by substituting for reference point 45 a contact point or roller 65 resting lightly against plate 63, the gun fire may be electrically controlled.

The passing of the contact point back and forth across the space between curves WX and YZ may be made to close and open the firing circuit 66, or to light a lamp, to ring a buzzer, or otherwise prevent or warn against the firing of the gun or guns, when the error due to the trunnion tilt is greater than the permissible mount, as shown by the indicator 45, falling outside of the space between the lines WX and YZ.

By this invention I provide a method and means by which the errors caused by the tilting of the trunnions of naval guns may readily be compensated for. It has the distinct advantage of extraordinary simplicity. In order to accomplish this result it is necessary to establish a reference plane which always is parallel to the plane of the trajectory and this is easily and accurately done by means of a dead beat pendulum, or any of the other means mentioned above.

Having established such plane, the line of sight may be moved into, or parallel to it, very easily and quickly with the apparatus which I provide, and the source of the greatest error of trunnion tilting is corrected for because the line of sight now lies in a vertical plane parallel to the plane of the trajectory. By utilizing the connection shown in Fig. 3, fthe line of sight is depressed automatically, an amount depending upon the angle of tilt of the "trunnions, and hence compensate for both errors caused by trunnion tilting.

It might seem, at first thought, that with the second modification of my invention described above, that is, that of indicating transmet the error without correcting it would result in the slowing down of the rate of lire, but this is not the fact. In reality it results in an increase in rate of elfective fire, because any gun, or salvo, which would be tired, unless interrupted by my invention, would l'all outside the permissible limit of errorpossibly many ship lengths outside-and would be thus completely wasted. By preventing the fire in this way, another opportunity may come in three or four seconds, instead of only after perhaps halt a minute, which would represent the waste time if the salvo vfrom the main battery were thrown away-to say nothing of the enormous expense and waste of the comparatively short life of the big guns.

The changes which are required to be made in the apparatus now in use for sighting guns in order to embody the principles of my invention are relatively few, and the expense of the installation is consequently low. lVhen the alternative method of indicating the maximum permissible limits of error is adopted the expense of the installation is reduced to a minimum and accurate firing of the gun or guns is accomplished with a minimum of eiiort on the part of the operators of the gun.

In the above description, my invention is, for the sake of clearness and simplicity shown as applied directly to a gun mount, the necessary corrections of indications being obtained by the movements of the gun and sight. But on the modern battleships this direct application would only be practical on the guns of the secondary battery. The guns of the main battery, to which the application of trunnion tilt correction is of greatest importance, are enclosed in turrets and for various reasons the guns are rarely il ever, directed by means of sights mounted directly on a gun, but on the contrary, are elevated and trained as a result of orders or signals transmitted from a rections transmitted.electrically or mechanif.`

)really to tliepgun pointers in the turrets. A single dead beat pendulum can thus be made to simultaneously control the lire of any number of guns.

I claim:-

l. A gun sighting mechanism comprising, a gun mount, a sight yoke universally mounted thereon and means for adjusting said yoke in two planes at right angles to each other7 a sight rod mounted on the sight yoke and provided with a reference point, a dead beat e dului having an indicator in y 'W ""tli reference point, and means for adjusting the sight rod laterally with respect to the sight yoke to keep the reference point opposite the indicator.

2. A gun sighting mechanism comprising, a gun mount, a sight yoke universally mounted thereon and means for adjusting said yoke in two planes at right angles to each other, a sight rod mounted on the sight yoke and provided with a reference point, a dead beat pendulum having an indicator in proximity to the reference point, means for adjusting the sight rod laterally with respect to the sight yoke to keep the` reference point opposite the indicator, and means associated therewith for vertically depressing the sight rod by an amount proportional to the lateral movement.

In testimony whereof I aiiix my signature.

SAMUEL LIPPINCOTT GRlSWOLl) KNOX. 

